#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define srep(i, s, t) for (int i = s; i < t; ++i)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
#define MAX_N 200005

const int MAX = 1110000;
const int MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];
// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1]            = 1;
    for (int i = 2; i < MAX; i++) {
        fac[i]  = fac[i - 1] * i % MOD;
        inv[i]  = MOD - inv[MOD % i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
// 二項係数計算
long long COM(int n, int k) {
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

long long FINV(int n) {
    if (n < 0) return 0;
    return finv[n];
}

int main() {
    COMinit();
    int m;
    cin >> m;
    vector<int> v;
    int h;
    while (cin >> h) {
        v.push_back(h);
    }

    int n = v.size();

    int sum = 0;
    rep(i, n) sum += v[i];
    sum += n - 1;
    if (sum > m) {
        cout << "NA" << endl;
        return 0;
    }

    if (v[0] == 0) {
        cout << 1 << endl;
        return 0;
    }

    rep(i, n) {
        m -= v[i];
    }
    m++;

    int ans = COM(m, n);

    cout << ans << endl;
    return 0;
}